I've gotten rather sick of rolling myself under my car and coming out like a chimney sweep and getting gunk in my eyes so I'm looking for a good undercarriage steam cleaner in South OC. Any suggestions?

Do you have a full service car wash in your area? If you buy the delux package from them, it will usually include an undercarriage wash. If your car has oil leaks, you will probably want to do it just a day or two before you plan to crawl under it, since if you do it a few weeks in advance, the oil will be back when you get to crawl under it.

Yep, plenty of oil leaks on this aging L69 motor, but overall there is just tons of sludge caked everywhere under this car-- I don't know that it was ever cleaned underneath at all, and I want to make sure wherever I take it that these guys have the equipment to really attack all this buildup. I've heard that only a steam wash really does the job but not all places do that (including the places I've checked).

Find a coin car wash without a sign or cameras.
The HP hoses will clean it off. or spray it first with a wash off engine cleaner then hit it with the HP hose.

I just found a place in Anaheim that does undercarriage steam cleaning/engine cleaning for around $85. I'll post back if I decide to give it a shot. It just occured to me though that I'll probably have to PNO my car this coming year due to that bastard 'visible smoke test' law while I save up for a new engine, so maybe another 6 months of grime will be bearable. For anyone else interested, here's their info:

Tunex Auto Service
929 N. Anaheim Blvd.
Anaheim, Ca 92805
(714) 680-4846